The present invention relates broadly to methods and apparatus for napping a traveling fabric web and, more particularly, to a novel method and apparatus by which such napping operations may be repeatably controlled to achieve consistent napping results.
It is known to provide a textile fabric with a raised surface effect by brushing the fabric surface, commonly referred to as napping. A common type of conventional napping machine has a rotating cylinder with a plurality of rotating toothed rollers at the periphery of the cylinder. Typically, card clothing covers the periphery of the rollers. The card teeth may be arranged selectively to project in the same direction as, or counter to, the direction of roller rotation or alternating and intermediate rollers may be provided with oppositely projecting card teeth. In napping operation, a textile fabric web is directed to travel peripherally with respect to the rotating cylinder for napping engagement of the fabric surface by the teeth of the rotating rollers.
The napping effect of cylinder-type napping machines of this type may be varied by adjustment of a number of operating parameters, including the type of card clothing selected for the rotating rollers, the sequence of nap rollers having oppositely projecting card teeth, pretreatment of the fabric web such as by emerizing or chemical treatment, the traveling speed of the fabric web selected, the tension in the fabric web, adjustment of the rotational speed of the rollers, adjustment of the degree of slippage of the napping rollers with respect to their belt drive arrangement, the number of napping passes to which the fabric web is subjected, and lifting devices provided on the periphery of the cylinder. Normally, it is optimally desirable to perform a napping operation with the fabric web traveling at as high a speed as practical and with as few a number of napping passes of the fabric web as necessary to achieve the desired napping effect.
It is, of course, possible to preset or control all of the aforementioned operating parameters of a napping operation in order to provide optimal results. West German Patent No. 11 45 573 discloses a method for controlling various such operating parameters. However, no accepted standards and no known devices exist for precisely measuring the napping effect achieved in any given napping operation. Accordingly, the adjustment of operating parameters in a napping operation generally can be effectively accomplished only by an experienced technician and, even then, uniform napping results are only conditionally reproducible from one napping operation to another.